Which of the following is directly related to deep-ocean currents?
a. density
b. wind
c. temperature
d. salinity

The answer is:  [A]:  "density" .

 Put simply,  deep-ocean currents are, in fact, "deep",  and dense water sinks to the bottom (think "depth") and the denser water (compared to the "less dense" water) continues to sink as the (comparatively) less dense water rises.

This is the best answer choice.
 
(Note:  Indirectly, "salinity" is related, since salinity and density are proportional;  since the "saltier" the water in the ocean (not just sodium chloride—but other types of salts), the "DENSER" the water.
    Of course, "temperature" is indirectly related, since warmer water is LESS dense that cold water, and colder water is denser and sinks.

But "density" is DIRECTLY related to "deep-sea ocean currents" and is the correct answer choice.

d

step-by-step explanation:

an inequality is an expression which means more than one number is a solution. we graph the solutions on a number line to show all possible values. we graph using circles and arrows.

equal to and less/greater than are graphed with filled in circles on the value.only less/greater than (not equal to) are graphed with open (not filled in) circles on the value.we draw an arrow the direction the solutions satisfy the inequality. generally this is the direction the inequality itself points.

this is a filled in circle on -2 so this is . this means only answers c and d are options.

answer d points to the right.